The present invention relates to a superior apparatus and method for removing and replacing vehicular hydraulic fluid. In particular the present invention relates to an apparatus for removing and replacing (changing) the hydraulic brake fluid used in the brake system of an automobile, truck, recreational or other vehicle. In conjunction with replacing (changing) the hydraulic fluid the hydraulic system is flushed of contaminants such as air, water, degraded hydraulic fluid and particulates. Significantly, the present system and method can be carried out as a substantially closed system.
Modern motor vehicles have internally-expanding, hydraulically operated brakes. Hydraulic actuation is based on the natural law principle that a pressure exerted upon a liquid is transmitted uniformly in all directions. An internal expanding brake system typically comprises a main or master cylinder with a reserve fluid tank, wheel cylinders and connecting brake lines or pipes. Application of the brakes by depressing the brake pedal causes a piston in the master cylinder to move which in turn displaces a hydraulic brake fluid stored in the master cylinder and causes the brake fluid to move through the brake lines. A pump can be used to increase braking capacity. The displaced brake fluid transmits a pressure through the fluid filled brake lines to the wheel cylinders that actuate the brake shoe or pad. As a result brake shoes or pads are thrust against a brake drum to stop the vehicle's wheels. Brakes pads, shoes or discs apply a force to particular components, such as the brake drums or rotors, which rotate with the wheels. As much as 2,000 pounds PSI of hydraulic pressure may be exerted by the brakes on each of the four wheels to stop the vehicle. Brake fluid also acts as a lubricant for pistons, cylinders, seals and valves within the brake system.
The pressure in a hydraulic system can be generated by a hydraulic pump, such as by a geared pump, a piston pump or a vane pump, which delivers a fluid, such as oil, through a delivery pipe to a control valve.
Brake fluid is the liquid used in automotive hydraulic brake systems. Different brake systems can use different types of brake fluid. Desirable brake fluid characteristics include a high boiling temperature, a low freezing temperature, the ability to absorb moisture and a low tendency to bubble. If the brake fluid becomes contaminated, piston seals, hoses and other parts within the brake system may have to be replaced to prevent malfunction of the braking system. Brake fluid is corrosive to paint and its spillage can therefore affect a vehicle's finish. Additionally, inhalation of brake fluid fumes and contact with the skin can present a health hazard. It also is a very innocuous yet dangerous environmental hazard as it rapidly is absorbed into water stores without detection.
Common vehicular brake fluids have ratings such as DOT (Department of Transportation) 3,4 or 5. DOT 3 brake fluid is generally used for normal city driving, DOT 4 for mountain, trailer towing or frequent hard braking use and silicone based DOT 5 brake fluid for performance or racing vehicles. Essentially, the higher the DOT rating the higher the boiling point of the brake fluid. The higher the boiling point of the brake fluid, the more hygroscopic or water absorbing the brake fluid tends to be. A brake fluid with a 3% water content can have a boiling temperature 25% lower than a water free brake fluid has.
Additionally, at low temperatures the water absorbed by the brake fluid can form ice crystals which impedes free flow of the brake fluid. Thus, the presence of water causes both a lower boiling point, and ice to form at low temperature both of which can reduce brake function.
Additionally, oxygen in the air can oxidize the brake fluid, which also reduces its boiling point. Even without extreme temperatures the water absorbed by the brake fluid can cause brake components to rust and fail. Additionally the additive packages used in brake fluids to reduce oxidation, foaming and corrosion are denigrated by the presence of moisture.
Generally, automotive brake fluid should be replaced and the brake system flushed of contaminants when the moisture level in the brake fluid had reached about 3%, when contamination is present, or when the hydraulic fluid's inhibitor package has deteriorated.
Most brake fluids are clear, volatile, water-soluble liquids comprised of a mixture of several alcohols such as glycols. Silicone based (DOT 5) brake fluids are also known. Due to its volatile nature and easily absorbed constituents, inhalation of and/or contact with brake fluid is not advised and can be hazardous to one's health. It is known that alcohol can degrade rubber seals and hoses. Additionally, through use brake fluid can become discolored due to contamination from dirt and disintegrating rubber seals. As stated, brake fluid is hygroscopic and absorbs moisture from the air, which lowers its boiling point, and provides an opportunity for corrosion to start inside the brake system. A lower brake fluid boiling point can result in the brake fluid boiling during, i.e. a long downhill stretch of intermittent braking. If the brake fluid boils the bubbles created reduce brake effectiveness and causes brake fade ("soft brakes") because the gas formed absorbs foot pressure instead of transmitting it through the brake lines.
Particulate matter such as airborne dust and rubber seal fragments can also collect within the fluid filled brake lines preventing proper sealing of valves within the braking system.
To remove water and contaminants the brake fluid is periodically removed and replaced with new brake fluid, thereby restoring the brake fluid's heat capacity, corrosion resistance and braking efficiency. The drained brake fluid is not reused because of its contamination and also once exposed to the atmosphere, even if only for a brief period, significant amounts of water, air (with the oxidizing oxygen) and contaminants such as dust can be absorbed by the brake fluid. Even new brake fluid exposed to ambient air can absorb moisture resulting in an immediate loss of the brake fluid's effectiveness. As evidence, brake fluid manufacturers recommend proper disposal of the unused portion of brake fluid supplied in small cans to the consumer industry. This is due to the high probability that the fluid remaining in the can was contaminated during the time the can was open and the possibility that the can would not be properly sealed to prevent future contamination prior to it being used again.
Brake fluid can be tested to determine its viability, as by determining its water content by the method and apparatus disclosed by U.S. Pat. No. 5,028,144, which patent is incorporated herein in its entirety. The '144 patent does not disclose an apparatus for removing or replacing brake fluid.
Thus hydraulic fluid, which is central to operation of the brake system, is periodically replaced due to fluid deterioration and contamination. Many hydraulic fluids have volatile and/or toxic components, which can hinder removal and replacement of the fluid.
Typically, the entire hydraulic fluid is drained from the brake system and replaced with new fluid, the whole operation being carried out in an open-air environment whereby the fluid is exposed to the atmosphere as the brake system is being drained and new fluid is added. Unfortunately this known method can release pollutants into the air and exposes the operator to potentially harmful fluids and vapors. Additionally, no attempt is made to recycle or reuse any of the hydraulic fluid resulting in economic waste and fluid disposal problems. Furthermore, some states have imposed a fee for the collection and disposal of used brake fluid from automotive service centers and the brake fluid is typically collected into open containers.
Typically brake fluid is changed per the warranty requirements of the manufacturer or as recommended by automotive experts by examining the color of the brake fluid or by replacement after a predetermined period (i.e., after 18 to 24 months or after 30,000 miles of vehicle usage).
If desired, a brake fluid moisture water content, or corrosion test can be done quickly utilizing currently available technology. Test strips available from Wagner or Phoenix Systems can be inserted into a vehicle's brake fluid to determine both the type of brake fluid being used and its relative water and corrosion content. The test is performed much like a pH test in that a test strip is inserted into the hydraulic fluid and visually reviewed for the level of contamination. The test method uses samples taken from either the master cylinder or a brake cylinder. The above-described brake fluid test can be run quickly, typically taking less than 1 minute.
The prior art method of replacing brake fluid takes two people about 30 to 45 minutes to remove and replace the brake fluid. The prior art method also requires additional time to clean-up the resulting spillage that is essentially inherent in the prior art method. One commonly known method for removing and replacing a vehicle's hydraulic brake fluid and then removing air introduced into the brake lines by this two person, open system method is shown in FIG. 1.
Typically, about twice the volume of fluid the brake caliper can hold per wheel is used by the prior art method. Unfortunately, new brake fluid can become contaminated with moisture, air and particulates as soon as the brake fluid container is opened and poured into the brake system due to the typical open system method used to flush and replace used brake fluid.
What is needed therefore is an apparatus and method for safely removing fluid contaminants such as air, water and particulates and replacing hydraulic fluid from a vehicle or other equipment's hydraulic system without exposing the environment or the operator (harmful to humans) to hydraulic (brake) fluid. And for protectively store new brake fluid to prevent its contamination prior to use; and to provide proper containment for the waste hydraulic (brake) fluid being removed from the hydraulic system so it can be properly disposed.